An example of tetrahedral electron pair geometry (E. P. G.)
and molecular geometry is CH4. The carbon has 4 valence
electrons and thus needs 4 more electrons from four hydrogen
atoms to complete its octet. The hydrogen atoms are as far apart
as possible at 109obond angle. This is tetrahedral
geometry. The molecule is three dimensional.

Methane is the simplest hydrocarbon molecule present in natural
gas. This molecule provides the basis for the tetrahedral geometries
at each carbon in a hydrocarbon chain.

In this example, NH4+, the Lewis diagram
shows N at the center with no lone electron pairs. Contrast this
with ammonia, NH3, which does have a lone pair. The
fourth hydrogen bonds to the ammonia molecule as a hydrogen ion
(no electrons) bonding to the lone pair on the nitrogen.

This shows tetrahedral geometry for both the electron pair
geometry and the molecular geometry.

Ammonium ions are found in solutions of household ammonia
or window cleaner. It is also found as part of a solid as ammonium
nitrate in fertilizer.

In this example, PO43-, the Lewis diagram
shows phosphorus at the center with no lone electron pairs. The
phosphorus and and one oxygen are bonded through a double bond
which counts as "one electron pair". Hence the molecule
has four electron pairs and is tetrahedral.

Phosphates are found in certain types of rocks, which are
mined and converted to fertilizer. Plants need phosphate to grow
as it is incorporated in the DNA and RNA genetic molecules. Furthermore
phosphate is an important structural component of bones and teeth.